One.relative_identifier(
  1 != 2,
  key: 3 != 4
) != Two.relative_identifier(
  2 != 1,
  key: 4 != 3
)
One.relative_identifier(
  1 != 2,
  key: 3 != 4
)(
  4 != 5,
  key: 6 != 7
) == Two.relative_identifier(
  2 != 1,
  key: 4 != 3
)(
  5 != 4,
  key: 7 != 6
)
One.relative_identifier key: 1 != 2
One.relative_identifier unqualified 1 != 2,
                                    key: 3 != 4
One.relative_identifier 1 != 2,
                        key: 3 != 4